The present invention relates to a halogen-free flameproof mesh sheet used outdoors, for example, at a construction site, for a long time.
In recent years, the height or number of stories of buildings is being increased in the construction industry. Meanwhile, the number of houses having a small number of stories is being increased. There buildings or houses must be covered with flameproof mesh sheets for safety and protection, flameproof mesh sheets for few-storied houses, and scattering prevention flameproof mesh sheets, and such regulations are becoming more and more strict.
Currently used flameproof mesh sheets and scattering prevention flameproof mesh sheets are produced by coating multifilament fibers of, for example, polyester, nylon or polypropylene, with a vinyl chloride-based paste resin composition, to prepare original yarn, which is then heated, and, after weaving the yarn into a cloth, heating the cloth to provide a mesh sheet. In another method, a mesh sheet is produced by coating a fabric prepared by weaving multifilament fibers with a vinyl chloride-based paste resin composition, heating the coated fabric, and then forming it into a desired shape.
In the resin composition with which the fibers and fabric are coated, a vinyl chloride resin containing chlorine is used as a resin, and a chlorine-based flame retardant such as chlorinated paraffin, bromine-based flame retardant such as decabromodiphenyl oxide or inorganic flame retardant such as antimony trioxide is used as a flame retardant (as disclosed in Examined Japanese Patent Publication Nos. 52-41786, 53-18065 and 61-9430, Plastics, February, 1991).
In recent years, it has been globally demanded to avoid the use of resins and flame retardants containing elemental halogen which generates harmful gas at the time of combustion, from the viewpoint of the environmental preservation of the earth.
It is proposed in Japanese Laid-open Patent Publicationn No. 61-223045 that red phosphorus and ammonium polyphosphate are kneaded into polyolefin to prevent corrosion caused by halogen contained in a flame retardant made of a halogen-containing compound. However, there has not been known a flame retardant prepared by dispersing red phosphorus and ammonium phosphate in an aqueous dispersion of an ethylene-vinyl acetate copolymer, or an aqueous dispersion comprising the above aqueous dispersion and an aqueous dispersion of an .alpha.-olefin copolymer and/or an aqueous dispersion of polyurethane.
The inventor of the present invention has proposed in Japanese Patent Application No. 9-225464 a halogen-free flame retardant comprising an aqueous dispersion of a polyolefin resin as a flame retardant. This flame retardant yields an excellent effect, but its viscosity tends to increase due to chronological changes during storage thereof.
The inventor of the present invention has also proposed in Japanese Patent Application No. 9-312550 a halogen-free flame retardant comprising an aqueous dispersion of an ethylene-vinyl acetate copolymer containing 10 to 90 parts by weight of vinyl acetate. While this flame retardant has excellent effect and function, the present invention provides further improvements in the gloss, flexibility and flame retardancy over the proposed flame retardant. Flameproof mesh sheets having significantly improved gloss and flexibility have been strongly desired depending upon the field in which the sheets are used.